cab2

cab2, commonly written as CAB2, refers to a gene that encodes a chlorophyll a/b-binding protein in plants. It is a member of the light-harvesting complex II (LHCII) family, which forms part of the antenna system that captures light energy for photosystems in the chloroplast thylakoid membranes. The CAB gene family is widespread in land plants, and CAB2 is one of several chlorophyll-binding proteins that contribute to the efficiency of photosynthesis by funneling excitation energy toward the reaction centers.

Function and characteristics: The protein encoded by CAB2 is a small, hydrophobic component of the thylakoid membrane that binds chlorophyll a and b. By participating in light harvesting, CAB2 helps optimize energy transfer to photosystem II, working in concert with other CAB/LHCII proteins. Because of this redundancy, individual CAB genes often have overlapping roles, and alterations in one member may be compensated by others.

Regulation and expression: CAB2 expression is tightly regulated by light. It is typically upregulated rapidly upon exposure to light, reflecting its status as an early light-inducible gene in many plant species. Light quality, intensity, and circadian factors influence its transcription, making CAB2 a commonly used marker for studying light signaling pathways.

Genetic and experimental use: In model plants such as Arabidopsis thaliana, CAB2 is frequently used to investigate photomorphogenesis and chloroplast development. Its promoter is used in molecular biology constructs (for example, CAB2::GUS or CAB2::LUC) to monitor light-responsive gene activity.

Taxonomy and evolution: The CAB2 gene exists within a multigene family with multiple paralogs across plant species, reflecting diversification and partial functional redundancy among chlorophyll-binding proteins.

See also: Chlorophyll a/b-binding proteins, light-harvesting complex, photomorphogenesis.